Our home has a room converted from half of our garage that my husband uses as his "man cave". There's a really awkward closet that wasn't serving much of a purpose. So we worked with Ana White to come up with a door that also serves as a bookcase! And the best part? You can hardly tell it's a door! We chose to install a deadbolt and use the hidden closet for locking gun storage. It cost about $60 in lumber. For more photos and a link to the plans, you can see my post here
http://www.killerbdesigns.com/is-it-a-bookca...
This is great, Brooke! Hidden closets & rooms always appeal to this mystery junkie! :)